Electric heater



Aprifi 1929 c. ABBOTB" 11,78,951

ELECTRI C HEATER Original Filed July 6, 1926 Inventor: Cherries C.Abbott,

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Patented Apr. 16, 1929.

UNITED STATES- PATENT OFFICE.

CHARLES C. ABBOTT, OF PTTTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATER.

Original application filed July 6, 1926, Serial No. 120,562. Divided andthis application filed August 17,

1927. Serial My invention relates to electric heaters and has for itsobject the provision of a simple and rcliableconnection between aresistance conductor and a terminal member.

In carrying out my invention in one form I provide a slot in theterminal member and fold the end of the resistance conductor to providea plurality of lengths which are placed in the slot and secured thereinby pressing the sides of the slot together.

This application is a division of m copending application Serial No.120,562, filed July 6, 1926.

For a more complete understanding of my invention reference should behad to the accompanying drawing in which Fig. 1 is a view mainly insection of an electric heater embodying my invention; while Fig. 2 is asectional view of Fig. 1 taken along the line 2-2 looking in thedirection of the arrow; Fig. 3 is an enlarged sectionalview showing theelectric heating unit; Fig. 4 is a sectional view along the line 4-4 ofFig. 3.

Referring to the drawing, in carrying out my invention in one form Iprovide an electric heating unit comprising a metallic sheath or casing10, preferably tubular, in which a heating resistance element 11 issecured. As shown, the heating resistance 11 is a wire which is made ofa suitable material, such as a nickel chromium alloy. It is woundhelically on a cylindrical support 12 made of suitable electricallyinsulating material, such as lava. The ends of the resistance wire aresecured to metallic terminal members 18 and 14, which may be made of thesame material as the resistance wire, the terminal members beinginserted in longitudinal apertures or bores 13* and 14 provided for themin the support 12.

In order to provide for the connection of 1 the ends of theresistancewire with the terminal members 13 and 14, each terminal member isprovided with a longitudinal slot 15, Figs. 3 and 4, the two terminalmembers being identical in construction. This slot begins at one end ofthe terminal member and terminates just short of the other end. The endof the resistance wire is folded over to form two or more parallellengths which are twisted t -gether, as indicated by the numeral 16. Asshown, three lengths are twisted together. the groove 15 and then theside walls of the This twisted portion 16 is placed in groove arepressed together or peened over an intermediate section of the twistedportion, as indicated at 17 and 18. The ends of the twisted portionproject from the peened over walls of the groove, and, due to theconstriction of the intermediate length, effectively secure the twistedportion in place. As connected with the terminal member 14, theresistance wire extends from the open end of the groove, but in theterminal member 13 the twisted portion 16 is reversed so that the wirepasses out laterally from the opposite end of the groove, as shown inFig. 1.

In assembling the resistance Wire and terminals on the support 12, theresistance wire is secured to the terminal 14, and the terminal 14inserted in its aperture 14, the resistance wire being laid in alongitudinal groove 19 provided for it in the support 12 and brought tothe opposite end of the support where it is laid in a cross groove 20 inthe support and brought out at the opposite side. The resistance wire isthen wound helically on the support toward the opposite end andsufficient slack is left in the resistance wire after the windingoperation to permit the terminal 13 to be connected as previouslydescribed and then inserted in its aperture 13 in the support,the'resistance wire extending through a longitudinal slot 21 in thesupport. After the terminal 13 has been put in place the resistance wireis tightened by twisting the terminal one or more revolutions, wherebyone or more turns of the resistance Wire are wound around the terminal13 to take up the slack. The edges of the groove 15 are rounded off at15 and 15 at the region where the wire is brought out laterally, inconnection with terminal memben13, so that the wire will not be injuredwhen wound on to take up. the slack. This form" of connection provides avery reliable mechanical and electrical joint and also allows theresistor to be readily assembled on the support 12.

The core 12 with the resistance wire there on is embedded in the sheath'10 in powdered heat refractory insulating material 22, such asmagnesium oxide, which is preferably compacted so as to secure the coreand heating resistance in place and also to increase the heatconductivity of the powdered material. As shown in the drawing, theturns of the resistance wire are suitably spaced apart on the core, thepowdered insulating material being packed between the turns. Thiscompacting operation may be carried out in any suitable manner, forexample by reducing the diameter of the sheath, as by swaging orrolling, after the unit has been assembled.

The end of the sheath opposite the terminal members 13 and 14 is closedby means of a metallic washer 23, the end of the sheath being spun overto secure the washer in place. In the opposite or terminal end of thesheath is a washer 24 made of insulating material, such as mica, and aporcelain insulator 25, apertures being provided in the washer andinsulator for the protruding end lengths 26 and 27 of the terminalmembers. To im prove their flexibility the lengths 26 and 27 may be madeof twisted wire. As shown, these protruding ends or terminals aresomewhat smaller than the terminal member por tions inside the unit, ashoulder being thereby formed at the junction of the two portions onwhich the insulating washer 24 is seated. The end of the sheath 10 isspun over a shoulder 28 provided on the insulator 25. In addition toacting as an insulator, the washer 24 acts as a cushion or bufier toprevent cracking of the porcelain insulator 25 from the end pressurecaused by the swaging operation.

While I have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should be understood that I do not limit myinvention thereto, since various modifications thereof will suggestthemselves to those skilled in the art without departing from the spiritof my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The method of securing a resistance conductor to a metallic terminalmember which consists in providing a longitudinal groove in theterminalmeniber, folding the conductor to provide a plurality oflengths, placing said lengths in said groove, and then compressing thesides of the groove on said lengths to secure the resistance-conductorto said terminal member.

. 2. The method of securing a resistance wire to a metallic terminalmember which consists in providing a longitudinal groove in the terminalmember, twisting lengths of the wire together, placing said twistedportion in said groove, and then squeezing the sides of said groovetogether on said twisted portion.

3. The method of securing a resistance wire to a metallic terminalmember which consists in twisting lengths of said wire together, andthen compressing the metal of said terminal around said twisted portion.

4. The method of securing a resistance wire to a metallic terminalmember which consists in twisting lengths of said wire together, andthen compressing the metal of said terminal member around a centralsection of said twisted portion.

5. The method of securing a heating resistance wire to a terminal memberwhich consists in providing a longitudinal groove in the terminalmember, folding the wire to form a plurality of parallel lengths,twisting said lengths, laying said lengths in said groove, and thensqueezing the sides of said groove together on said twisted portion.

6. In an electric heater, a terminal member provided with a groove, anda resistance conductor provided with folded lengths laid in said groove,the walls of said groove being compressed in said lengths to secure theresistance conductor to said terminal.

7. In an electric heater, a terminal member provided with a groove, anda resistance conductor provided with folded twisted lengths laid in saidgroove, the walls of said groove being compressed in said lengths tosecure the resistance conductor to said terminal.

8. In an electric heater, a terminal member provided with a longitudinalslot, a resistance conductor provided with folded twisted lengths laidin said slot, the walls of said slot being compressed on said lengths tosecure said resistance conductor to said terminal member. 3

In witness whereof, I have hereunto set my hand this 15th day of August,1927.

CHARLES C. ABBOTT.

